How can I enable multiple selections without an app using the 'Buy Button'?

[NickBreal]

I'm using the Shopify 'Buy Button' on a 3rd party website, it works as intended BUT I have a few products that require multiple selections vs. one single variable. I realize certain apps can allow this functionality ...

HOWEVER None of the app functionality works when using the 'Buy Button'.

Is it possible to modify the embed code to allow for multiple selections? Is there a way to accomplish? I appreciate any help - stuck.

Thx